<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>Java后端WebSocket的Tomcat实现</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
</head>

<body>
    <div id="message"></div>
    <hr />
    <div id="main"></div>
    <div id="client"></div>
    <input id="text" type="text" />
    <button onclick="send()">发送消息</button>
    <hr />
    <button onclick="closeWebSocket()">关闭WebSocket连接</button>
</body>
<script type="text/javascript">

    var cid = Math.floor(Math.random() * 100); // 随机生成客户端id
    document.getElementById('client').innerHTML += "客户端 id = " + cid + '<br/>';

    var websocket = null;

    //判断当前浏览器是否支持WebSocket
    if ('WebSocket' in window) {
        // 改成你的地址
        websocket = new WebSocket("ws://127.0.0.1:8080/ws/" + cid);
    } else {
        alert('当前浏览器 Not support websocket')
    }

    //连接发生错误的回调方法
    websocket.onerror = function () {
        setMessageInnerHTML("websocket.onerror: WebSocket连接发生错误");
    };

    //连接成功建立的回调方法
    websocket.onopen = function () {
        setMessageInnerHTML("websocket.onopen: WebSocket连接成功");
    }

    //接收到消息的回调方法
    websocket.onmessage = function (event) {
        setMessageInnerHTML("websocket.onmessage: " + event.data);
    }

    //连接关闭的回调方法
    websocket.onclose = function () {
        setMessageInnerHTML("websocket.onclose: WebSocket连接关闭");
    }

    //监听窗口关闭事件，当窗口关闭时，主动去关闭websocket连接，防止连接还没断开就关闭窗口，server端会抛异常。
    window.onbeforeunload = function () {
        closeWebSocket();
    }

    //将消息显示在网页上
    function setMessageInnerHTML(innerHTML) {
        document.getElementById('message').innerHTML += innerHTML + '<br/>';
    }

    //关闭WebSocket连接
    function closeWebSocket() {
        websocket.close();
        alert('websocket.close: 关闭websocket连接')
    }

    //发送消息
    function send() {
        var message = document.getElementById('text').value;
        try {
            websocket.send('{"msg":"' + message + '"}');
        } catch (err) {
            console.error("websocket.send: " + message + " 失败");
        }
    }
</script>

</html>
